1. Field of the Invention
The present invention generally relates to rack structure bodies for machines, and more particularly, to a rack structure body on which an electronic machine is mounted, for example.
2. Description of the Related Art
Generally, a communication apparatus, an electronic machine such as a computer, a calculating machine, or the like; an apparatus for supplying electric power to the communication apparatus and the electronic machine (for example, an electric power supply apparatus where a battery for arc welding is installed), or the like is installed in a rack structure body consisting of various frames and racks. Recently and continuing, there is a tendency that parts forming the above mentioned electronic machine or electric power supply apparatus are installed in the machine or apparatus with high density, so that the machine or the apparatus is heavy.
FIG. 1 is an exploded perspective view showing a structure of a related art communication apparatus.
Referring to FIG. 1, a related art communication apparatus 10 has a structure wherein a plurality of shelves 12 are provided in a rack structure body 11. A lot of units 13, comprising electronic circuit boards or the like on which electronic parts are provided at high density, are inserted into the shelves 12. The rack structure body 11 includes a ceiling part frame body 21, a floor part frame body 22, two pieces of front surface side frame bodies 23, two pieces of back surface side frame bodies 24, and the like.
The whole weight of the communication apparatus 10, including the shelves 12 and the rack structure body 11, is supported by the rack structure body 11. The shelf 12 is installed at the front surface side frame body 23 so as to be provided inside of the rack structure body 11. Reinforcement members 14 are installed in the rack structure body 11 so as to reinforce the rack structure body 11.
FIG. 2 is a perspective view showing a structure of the rack structure body 11 shown in FIG. 1. FIG. 3 is an exploded perspective view showing the structure of the rack structure body 11 shown in FIG. 1. FIG. 4 is a cross-sectional view taken along the line A—A shown in FIG. 3.
Referring to FIG. 2 and FIG. 3, the ceiling part frame body 21 and the floor part frame body 22 have roughly rectangular and hollow configurations in the Z1–Z2 direction. The ceiling part frame body 21 and the floor part frame body 22 are provided so as to face each other. Two pieces of the front surface side frame bodies 23 are fit into two corner parts of front surface sides (Y2 side) of the ceiling part frame body 21 and the floor part frame body 22 in the Z1–Z2 direction. Two pieces of the back surface side frame bodies 24 are fit into two corner parts of back surface sides (Y1 side) of the ceiling part frame body 21 and the floor part frame body 22 in the Z1–Z2 direction.
The front surface side frame body 23 and the back surface side frame body 24 have substantially equal lengths in the Z1–Z2 direction. However, the front surface side frame body 23 and the back surface side frame body 24 are different in the following features. That is, referring to FIG. 4, the front surface side frame body 23 has a cross-sectional configuration in the X-Y plane in that continuous concave and convex parts are seen from inside parts of the ceiling part frame body 21 and the floor part frame body 22. The concave and convex parts are formed by bending. On the other hand, the back surface side frame body 24 has a cross-sectional configuration in the X-Y plane in that a side facing the inside of the ceiling part frame body 21 and the floor part frame body 22 is opened so as to form a “]” shaped configuration.
Furthermore, referring back to FIG. 2 and FIG. 3, a plurality of installation hole parts 29 are formed at the front surface side (Y2 side) of the front surface side frame body 23 in the Z1–Z2 direction. The installation hole parts 29 are used for installing the shelf 12 into the inside of the rack structure body 11 by screws or the like.
The above mentioned rack structure body 11 is assembled as follows. That is, first of all, two of the front surface side frame bodies 23 and two of back surface side frame bodies 24 are provided between the ceiling part frame body 21 and the floor part frame body 22. Next, the ceiling part frame body 21 and the two front surface side frame bodies 23, the ceiling part frame body 21 and the two back surface side frame bodies 24, the floor part frame body 22 and the two front surface side frame bodies 23, and the floor part frame body, 22 and the two back surface side frame bodies 24 are respectively positioned by a plurality of rivets 25, so that pre-assembling is done.
After that, as shown in FIG. 2, welding is performed at the whole circumferences (shown by numerical reference 26 in FIG. 2) of surfaces, where the ceiling part frame body 21 and the floor part frame body 22 face and the front surface side frame bodies 23 and the back surface side frame bodies 24 are connected, so that the rack structure body 11 is assembled.
Furthermore, welding is also performed in the Z1–Z2 direction at a part (shown by numerical reference 27 in FIG. 3), where surfaces in the X-Z and Y-Z planes of the ceiling part frame body 21 and the floor part frame body 22 come in contact with each other so that strengths of the ceiling part frame body 21 and the floor part frame body 22 can be improved.
According to other related art, there is a rack including a side surface board by which a pair of front and rear rectangular frames are connected.
According to further other related art, there is a casing body having a structure wherein a pair of vertical frames made of metal plates are connected by horizontal plates.
However, according to the rack structure body 11 of the above mentioned related art communication apparatus 10, it may be difficult to sufficiently correspond to the heavy weight of the communication apparatus 10 based on the heavy weight of the parts that are provided in the communication apparatus 10 with high density.
That is, if the width of the front surface side frame bodies 23 or the back surface side frame bodies 24 is increased or reinforcement metal fittings are further provided so as to improve the structural strength of the rack structure body 11 for corresponding to the heavy weight of the communication apparatus 10, the weight of the rack structure body 11 is increased.
For example, since the shelf 13 shown in FIG. 1 is inserted from the front surface side of the communication apparatus 10 to the back side surface side of the communication apparatus 10, namely from the Y2 side to the Y1 side so as be provided in the communication apparatus 10, stress is concentrated at the front surface side, namely the Y2 side. If the width of the front surface side frame bodies 23 is made greater in order to solve the above mentioned problem, the weight of the rack structure body 11 is increased.
Meanwhile, an allowable floor load, that is an allowable value of a floor load applied by the rack structure body 11, for example approximately 300 [kg], is prescribed for the floor part where the rack structure body 11 is provided. In a case where the load exceeds the above mentioned allowable floor load, it may be impossible to provide the rack structure body 11 on the floor part.
Furthermore, in a case where the weight of the rack structure body 11 is increased without strengthening the rack structure body 11, if some external force is applied so that vibration of the frame structure body 11 occurs, displacement value in the X1–X2 direction of FIG. 2 is made large, for example.
If the displacement occurs so that the displacement value exceeds an allowable displacement standard value (for example, approximately 50 [mm]), the rack structure body 11 may come in contact with other apparatuses which stand close to the rack structure body 11. Furthermore, if the applied stress exceeds allowable stress of materials for the rack structure body 11, the rack structure body 11 may be broken.
Furthermore, if the weight of the rack structure body 11 is increased, a characteristic frequency of the rack structure body 11 is made small and may be lower than a designated characteristic frequency, for example approximately 7[Hz]. As a result of this, the characteristic frequency of the rack structure body 11 may agree with an earthquake wave frequency ingredient having a value less than approximately 10 [Hz] or 7 [Hz], so that the communication apparatus 10 is resonated and therefore resistance to earthquakes of the communication apparatus 10 may be degraded.
Meanwhile, it is necessary to secure sufficient space to provide for the shelf 12 shown in FIG. 1. Hence, it is ideal that the frontage of the rack structure body 11, namely the space between two of the front surface side frame bodies 23 which face each other be made large; and width L, namely the length in the X1–X2 direction of the front surface side frame bodies 23 will thereby be shortened.
However, in the related art rack structure body 11 shown in FIG. 1 through FIG. 3, if the width L, namely the length in the X1–X2 direction of the front surface side frame bodies 23 is shortened, the strength of the rack structure body 11 is made low. Structural opposing means against displacement in the X1–X2 direction of the rack structure body 11 are mainly the ceiling part frame body 21 and the floor part frame body 22. Hence, if the width L, namely the length in the X1–X2 direction of the front surface side frame bodies 23 is shortened, the strength in the X1–X2 direction of the rack structure body 11 is lowered so that the amount of the displacement in the X1–X2 direction is made large due to vibration and others. Under the above mentioned structure, stress concentrates at a part where the ceiling part frame body 21, the floor part frame body 22, and the front surface side frame bodies 23 come in contact and welding is performed, namely the part circled by a dotted line and shown by numerical reference 26 in FIG. 2.
Furthermore, if the above mentioned welding is performed, heat stress or the like due to the welding occurs. This causes a decrease of the measurement precision of the positions of the installation hole parts 29 formed at the front surface side (Y2 side) of the front surface side frame body 23, namely assembling measurement precision of the rack structure body 11. Furthermore, this requires skill and experience for assembling the rack structure body 11, takes a lot of time for assembling, and causes an increase of manufacturing cost.
In addition, since electrical wiring having a designated length is used for the communication apparatus 10, it is necessary to secure space at the rack structure body where the electrical wiring can be provided.